Scales of Measurement
Measurement is the foundation of research study, everything a researcher undertakes starts with measurement. The mathematical properties of the variables we analyze are important because they determine which mathematical operations are allowed. This, in turn, determines which statistics we can use with those numbers. Statistical tests are applied depending on what scale the variable measures on.
Scales of measurement are rules that describe the properties of numbers. Variables have different numerical strength, based on their numerical strength a suitable scale of measurement is assigned to the variables under study. In all, scales of measurement are characterized by four properties:
- Identity means that each number has a particular meaning.
- Magnitude means that numbers have an inherent order from smaller to larger.
- Equal intervals means that the differences between numbers (units) anywhere on the scale are the same (e.g., the difference between 4 and 5 is the same as the difference between 76 and 77).
- Absolute/true zero means that the zero point represents the absence of the property being measured (e.g., no money, no behavior, none correct).